Invasive plants add to fire danger


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Fan palms and other invasive species that dot San Diego County’s landscape may be nice to look at but they can be factors in the spread of wildfires, officials say.

They’re not the only culprit in an area where native plants like coastal sage and chaparral dry out when whether warms up. But there are ways to reduce the hazards.

Tom Clancy, a certified arborist from the International Society of Arbor Culture and an independent consulting arborist, said the popular Mexican fan palms - a plant native to northern Mexico whose scientific name is Washingtonia Robusta - is an example of a plant that can be particularly dangerous in a fire.

Often when the trees are pruned, the remaining part, which is known as the tree’s “boot,” can dry up and become highly flammable, he explained. During a fire, the boots can become especially dangerous when they catch fire and detach, often landing on surrounding structures and plant life.

“They essentially become flaming flying Frisbees,” said Clancy. He also said that Mexican fan palms are on the California Invasive Plant Council list of species, which includes plants and trees that are very prolific and spread easily, crowding out other native vegetation.

Clancy advises home and business owners not to plant the fan palms at all or to remove existing plants. If this is not an option, it is best that the trees be skinned and that the boot removed, which tree care companies can do. In addition, the trunks of tree species of all types should be skinned on a regular basis, as the loose bark can easily catch fire from nearby flames and embers.

Maurice Luque of the San Diego Fire-Rescue Department said that in a fire storm all vegetation is capable of burning, even ice plant.

Here are some steps that can be taken to lessen the fire hazard of plant life.

  • Trim lower tree limbs on a regular basis.
  • Take care not to have hanging branches on the roof.
  • Care should also be taken not to have any tree branches closer than 10 feet to a chimney, and tree branches that hang over a structure should be cleared of dead wood.
  • As a general rule, there should be 100 feet of space around a home where there are no trees.
  • Brush should also be thinned away from the house because this allows firefighters easier access and reduces fuel for the fire.

According to the city’s brush management regulations, in Zone 1 - 35 feet around the structure, - brush should be low growing, and with the exception of trees, should not stand above four feet.
In Zone 2 - the next 30 feet away from the structure - there cannot be any permanent irrigation and vegetation must be thinned and pruned seasonally.

Step one of is removing dead wood and invasive plant species.

Step two, thinning the vegetation, involves cutting half of the plants over two feet in height down to six inches. Trees and other plants higher than four feet should also be cut into an umbrella shape. This not only keeps the plant healthy and discourages weed and other plant growth underneath the plant, but also enables one to see what is growing underneath. Thinning and pruning should be done on a yearly basis.

For more information about the fire safety of vegetation and detailed instructions of thinning and pruning, visit the San Diego Fire-Rescue Department’s Web site’s page on brush management at

For a complete list of invasive plant species, visit the California Invasive Plant Council’s Web site at